1. Field of the Invention
This invention generally relates to hot water dispensers and methods of making beverages and other foods that require mixing with hot water at different temperatures and, more particularly, to an electrically powered, automatic hot water dispenser in which the serving temperature of the hot water may be selectively changed on-demand and a method of serving hot water at different temperatures on demand from a single hot water dispenser.
2. Discussion of the Prior Art
Electrical hot water dispensers are well known for use in dispensing hot water at different selected temperatures required for mixing with different food ingredients. For instance, in a tea room, optimum brewing of one type of tea or coffee may require one temperature while a different type of tea may require a lower temperature. Different temperatures may also be needed for preparation of food products, yeast, cocoa, etc.
While known hot water dispensers may be capable of dispensing hot water at different temperatures, a problem with known dispensers is that changing the temperature of the hot water being dispensed from one level to another takes too long accommodate making drinks requiring different optimal water temperatures on demand. Thus, in some dispensers, while the temperature may be changed over several or more minutes, it is not changeable on demand in seconds or fractions of seconds. Consequently, it is known in coffee and tea shops and the like to maintain three or four hot water dispensers with the water in the hot water tanks of each kept at different selected temperatures. Alternatively, some use very high temperature water and manually dilute it by adding cooler water, which creates a hot water handling risk plus adds additional steps to the tea making process. This disadvantageously requires additional counter top space in addition to the multiplication of costs for acquisition, operation and maintenance of a plurality of such dispensers.
In other adjustable hot water dispensers, it is know to mix water from two different sources at different temperatures, such as two separate hot water tanks in the same dispenser, but still such mixing is often still much to slow for rapid dispensing of water at significantly different temperatures and often the mixing rations and temperature are poorly controlled such that the desired dispense temperature is not obtained or not obtained on a reliable basis.
Most water temperature proportioning are mechanical water blenders or use a flow proportioning orifice to mix water at different temperature which results in imprecise temperature control which can result in undesirable results when brewing quality tea or coffee. The methods of mechanical mixing, either thermostatically or electronically, are all subject to an undesirable offset in control caused by an off-differential, or “hysteresis”.